JPH0220452A - Control of differential control clutch for front and rear wheel driving vehicle - Google Patents

Abstract

PURPOSE:To improve the control precision by making rough the step variation characteristics alternatively having the restraint range and the variation range of the differential restraint force of a differential control clutch when the variation rate of the driving state parameter is high, and making fine when the variation rate is low. CONSTITUTION:Based on the driving state parameter of a vehicle detected by various sensors, a controller 86 controls the front and rear wheel differential restraint force according to the step variation characteristics alternatively having the variation restraint range where variation in the restraint force used to restrain the differential operation of front wheels 24 and rear wheels 28 by a differential control clutch 82 is restrained, and the variation range where such restraint force is varied quickly. In such control method, when the changing of driving state parameters is increased, the step variation characteristics is made rough and when the rate is reduced, the characteristics is made fine. Thus the durability of both the differential control clutch 82 which operates a torque distribution differential gear 20 and the oil pressure control circuit 84 of said clutch 82 is improved and meanwhile, when the changing rate of the driving state parameters is low, the control precision of the differential restraint force may be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a front and rear wheel drive vehicle equipped with a differential control clutch that adjusts the differential rotational speed of front wheels and rear wheels. The present invention relates to a method and apparatus for controlling limiting force.

BACKGROUND ART In a front-wheel drive vehicle such as a four-wheel drive vehicle, a switch is used to selectively connect one of a front-wheel drive member and a rear-wheel drive member to the other to switch between a two-wheel drive state and a four-wheel drive state. So-called vert time type ones equipped with a clutch,
There are so-called full-time types that are equipped with a differential limiting clutch for limiting the differential operation of a center differential device that distributes drive torque between front wheel drive members and rear wheel drive members. The switching clutch and the differential limiting clutch as described above are called differential control clutches because they adjust the differential rotational speed between the front and rear wheels by controlling their differential limiting force.

A differential control clutch such as the one described in 2 is based on vehicle driving condition parameters such as vehicle driving force, front and rear wheel differential rotation speed, steering angle, throttle valve opening, and vehicle speed from pre-prepared relationships. The differential limiting force is controlled. The above relationship is
For example, as described in Japanese Unexamined Patent Publication No. 63-57332, a stepped shape is used.

Problem to be Solved by the Invention By the way, in the differential control clutch control device as described in "-", the relationship used to control the differential limiting force of the differential control clutch is changed in a stepwise manner. 11. Therefore, the above-mentioned driving condition parameters change pulsatingly. However, the fine movement of the hydraulic servo mechanism for operating the differential control clutch, such as the piston of the hydraulic i' actuator and the control valve that supplies control hydraulic pressure to it, is eliminated.
Although they have the advantage of increasing their durability, it is inevitable that the differential limiting force of the differential control clutch will be roughly controlled and the control accuracy will be reduced.

The present invention has been made against the background of the above circumstances, and its object is to change the relationship used to control the differential limiting force of the differential control clutch in a stepwise manner. The object of the present invention is to provide a control device that can control the differential limiting force of a differential control clutch as accurately as possible.

Means for Solving the Problems In order to achieve the above object, the gist of the present invention is to provide a front-wheel drive vehicle of the type equipped with a differential control clutch that adjusts the differential rotational speed of the front wheels and the rear wheels. , an inhibitor for suppressing a change in the differential limiting force of the differential control clutch;
A control method for controlling the differential limiting force based on a vehicle running condition parameter based on a relationship having a step-like change characteristic that alternately has a region and a changing region that rapidly changes the differential limiting force, The stepwise change characteristic of the relationship is coarsened when the speed of change of the driving condition parameter becomes large, and the stepwise change characteristic of the relationship is made narrower when the speed of change of the driving condition parameter becomes small.

In this manner, the step-like change characteristic of the relationship becomes rougher as the speed of change of the driving condition parameter increases, and the step-like change characteristic of the relationship becomes finer as the speed of change of the driving condition parameter decreases. Therefore, the accuracy of differential limiting force control of the differential control clutch can be increased as much as possible. Naturally, when the speed of change of the driving condition parameters is large, the differential limiting force of the differential control clutch changes frequently, so in such conditions, the relationship used to control the differential limiting force changes stepwise. While the characteristic is coarsened to increase the durability of the hydraulic servomechanism for operating the torque distribution clutch, the differential limiting force cannot be changed frequently when the speed of change of the driving condition parameters is small, so that step-like changes are avoided. There is no problem even if the characteristics are made finer, and this increases the degree of control of the differential limiting force.

Here, as the driving state parameters of the vehicle, the driving force of the vehicle, the differential rotational speed of the front and rear wheels, the steering angle, the throttle valve opening, the vehicle speed, etc. are suitably used.

In this case, the relationships for controlling the differential limiting force of the torque distribution clutch include the driving force of the vehicle, the differential rotational speed of the front and rear wheels, the steering angle, the throttle valve opening, the vehicle speed, etc. At least one function.

In addition,...I-memory related step-like change characteristics usually have a horizontal width corresponding to a suppression area that suppresses changes in the differential limiting force,
The rise width corresponding to the change region in which the differential limiting force is rapidly changed is increased as the speed of change of the running condition parameter increases, and is decreased as the speed of change decreases, thereby creating a staircase. The shape change characteristics are made coarser or finer. In this case, preferably, the step rate of change (one vertical width/horizontal width) of the step-like change characteristic is kept constant, and the step-like change characteristic is made coarser or finer.

EXAMPLE Hereinafter, an application example of the present invention will be explained in detail based on the drawings.

FIG. 1 is a diagram showing a power transmission system, a control device for a differential control clutch 82, etc. of a transverse engine four-wheel drive vehicle. In the figure, the output of engine 10 is supplied to automatic transmission 614 via clutch 12. This clutch I2
It consists of a torque converter, fluid coupling, magnetic particle electromagnetic clutch, hydraulic multi-disc clutch, etc. The automatic transmission 14 is constituted by, for example, a planetary gear type transmission, and includes four forward speeds and one reverse speed. The automatic transmission 14 is provided with a hydraulic control circuit 16, and a plurality of l'!
! By selectively operating the frictional engagement device by the hydraulic control circuit 16, the gear stage is automatically switched.

The driving torque output from the automatic transmission 14 is divided into two by the center differential device 20, one driving torque is transmitted to the front wheels 24 via the front wheel differential device 22, and the other driving torque is transmitted to the rear wheels. The signal is transmitted to the rear wheels 28 via the wheel differential device 2G.

The center differential device 20 is the automatic transmission 14
A differential case 32 is integrally provided with an input gear 30 that meshes with the output gear 18 of the output gear 18, and is rotatable around one axis, and a binion shaft 34 is mounted in the differential case 32 in a direction perpendicular to the above-mentioned axis. A pair of differential small gears 36 and 38 that are rotatably supported, and a large differential gear 4 for front wheels that is meshed with the differential small gears 36 and 38, respectively.
0 and a large differential gear 42 for rear wheels, the automatic transmission 1
The drive torque input through the output gear 18 of No. 4 is distributed to the front wheel differential gear 40 and the rear wheel differential gear 42.

The front wheel differential device 22 includes a differential case 46 that is connected to the front wheel differential large gear 40 via a hollow front wheel drive shaft 44 and is rotatable around the -axis, and this differential case. 4
6, a pair of differential pinions 50 and 52 each rotatably supported by a binion shaft 48 mounted in a direction perpendicular to the above-mentioned axis;
0 and 52, respectively.
It is distributed to the left and right front wheels 24 via.

The driving torque transmitted through the rear wheel differential gear 42 of the center differential device 20 is transmitted to a bevel gear 58 fixed to the rear wheel differential gear 42, a bevel gear 60 that meshes with the bevel gear 58, and a universal gear at both ends. It is transmitted to a bevel gear 64 via a rear wheel drive rotor shaft 62 equipped with a joint. The bevel gear 58, the bevel gear 60, the propeller shaft 62, and the bevel gear 64 are a transformer Noah device for transmitting the driving torque for driving the rear wheels 28 from the center differential device 20 to the rear wheel differential device 2G. 66, and the bevel gear 64 functions as an output gear of the transfer device 66.

The rear wheel differential device 26 includes the bevel gear 64
a differential case 70 equipped with a ring gear 68 that meshes with the differential case 70; a pair of differential pinions 74 and 76 rotatably supported by a binion shaft 72 attached to the differential case 70; and the differential pinions 74 and 76. and a pair of differential large gears 78 and 80 that are meshed with each other, and distributes the driving torque transmitted through the transfer device 66 to the left and right rear wheels 28 via the pair of differential large gears 78 and 80. do.

A differential control clutch 82 is provided between the differential case 32, which functions as an input member of the center differential device 20, and the front wheel drive shaft 44, which functions as an output member of the center differential device 20. This differential control clutch 82 is configured, for example, by a wet multi-plate hydraulic clutch, and when the differential limiting force of the differential control clutch 82 is zero, it is used for differential operation between the front and rear wheels by the center differential device 20, i.e. Torque distribution is permitted, but as the differential limiting force increases, the center differential device 20
The torque distribution action of the center differential device 372 is limited and the differential control clutch 82 is fully engaged.
The differential case 32 and the large differential gear 40 are integrally connected to prevent torque distribution.

The clutch hydraulic control circuit 84 supplies hydraulic oil to a hydraulic actuator 90 for driving the differential control clutch 82 or discharges hydraulic oil from the hydraulic actuator 90 in response to a command signal from an electronic control device 86. to adjust the differential limiting force of the differential control clutch 82. As shown in detail in FIG. 2, the hydraulic actuator 90
A piston 95 that forms a hydraulic chamber 93 by being slidably fitted into a cylinder bore 91;
and a return spring 97 that biases the hydraulic chamber 9.
The piston 95 is configured to press the friction plate of the differential control clutch 82 as the working oil pressure in the differential control clutch 82 increases. The clutch hydraulic pressure control circuit 84 also includes a pressure regulating valve 94 that regulates the pressure of the hydraulic fluid pumped from the vehicle's hydraulic pump 92 to clutch hydraulic pressure, and supplies the clutch hydraulic pressure regulated by the pressure regulating valve 94 to the hydraulic actuator 90. The clutch control valve 98 is equipped with a clutch control valve 98 that continuously changes the differential limiting force of the differential control clutch 82 by draining hydraulic oil from the hydraulic actuator 90. For example, it is configured by a linear control valve (flow rate control servo valve) equipped with a linear solenoid that can continuously change the flow rate, or an on/off on/off valve that adjusts the flow rate by on/off control. In the case of a linear control valve, it is driven by an analog signal, and in the case of an on-off on-off valve, it is duty-controlled by an on-off signal.

The hydraulic pump 92 is rotationally driven by the engine 10 and also functions as a hydraulic pressure source for the hydraulic control circuit 16 of the automatic transmission 14.

The electronic control device 86 includes, for example, a brake sensor 100 that detects the braking state of the vehicle based on the brake oil pressure and the amount of operation of the operating pedal, a steering angle detection sensor 1, 02 that detects the steering angle of a steering wheel (not shown), and a vehicle body sensor. an acceleration sensor 104 that detects acceleration in the longitudinal and lateral directions;
A throttle sensor 106 that detects the throttle valve opening corresponding to the operation amount of the accelerator operation pedal, and an automatic transmission 14
a gear position sensor 108 that detects the actual gear position of the vehicle, a vehicle speed sensor 110 that detects the vehicle speed, and a front wheel rotational speed sensor 112.1 that detects the rotational speed of the pair of front wheels 24, respectively.
14, signals are supplied from a rear wheel rotation speed sensor 116 that detects the rotation speed of the rear wheels 28, and an engine rotation speed sensor 117 that detects the rotation speed of the engine IO.

The electronic control unit 86 is composed of a so-called microcomputer consisting of a CPU, RAM, and ROM, and has an RA
The hydraulic control circuit 16 processes input signals according to a program stored in advance in the ROM while utilizing the memory function of M.
and a mask cylinder 1 in which hydraulic pressure is generated by the clutch hydraulic control circuit 84 and the brake operation pedal 120.
A control signal is output to an anti-skid hydraulic control circuit 126 provided between the wheel cylinder 22 and the wheel cylinder 124.

That is, the electronic control device 86 determines, for example, the actual accelerator pedal operation amount, vehicle speed,
The gear stage of the G-C automatic transmission 14 is determined based on the operating position of the shift lever, etc., and a control signal for automatically switching to this gear stage is output to the hydraulic control circuit 16. Further, the electronic control device 86 detects the wheel rotational speeds of the left and right front wheels 24 and the rear wheels 28 according to a program (not shown), calculates an approximate vehicle speed from these rotational speeds, and calculates the approximate vehicle speed and wheel rotational speed. The slip rate is calculated from this, and the braking oil pressure to be supplied to each wheel cylinder 124 is determined from this slip rate and the wheel acceleration/deceleration, and a braking signal for obtaining this braking oil pressure is sent to the anti-skin 1' hydraulic control circuit 12G. Output. Further, the electronic control unit 86 constantly executes normal differential limiting force control according to a program (not shown), and controls the differential control clutch based on vehicle running state parameters from a relationship representing a predetermined change characteristic. A control signal for controlling the differential limiting force Fc of 82 is output to the clutch oil pressure control circuit 84.

Hereinafter, the main part of the control operation of the differential control clutch 82 will be explained using the flowchart of FIG. 3.

First, in step SAI, the driving force T of the vehicle is determined. That is, the actual engine rotation speed NF is read based on the signal from the engine rotation speed sensor 117, the actual throttle valve opening θ is read based on the signal from the throttle valve opening 106, and the gear position sensor 10B is read.
The gear ratio i of the actual automatic transmission I4 based on the signal from
is read, the actual driving force 1' is determined based on the engine rotational speed N, throttle valve opening θ, and gear ratio i of the automatic transmission I4, for example, from the following equations (1) and (2). Calculated by Note that the output torque 'rE of the engine 10 in equation (2) may be detected by a lux sensor.

T −= f (TE, r)
・ ・ ・(1) TE −f (NE ,
θ) ・ ・ ・ (2) In step SA2, drive is performed based on the current driving force T2 and the predetermined time Δ, which were obtained as described above from the following equation (3), and the previous driving force T. The force change rate ΔT/Δt is calculated.

8T/Δt= (T2 −TI)/Δt・・
(3) In step 5A34, it is determined whether the driving force change rate T/Δt determined in step SA2 is equal to or less than a predetermined criterion value a. Judgment reference value 81 in which T/Δt is predetermined for the rate of change of driving force
If it is determined that the above is the case, the change rate of the driving force is in a relatively steep region of T/Δt, so step SA4
In this step, the map A in FIG. 4 with the roughest step-like change characteristic is selected, and the differential limiting force FC is determined from the AI map based on the driving force T obtained in step SAI. . A plurality of types of maps are stored in advance in [20M of the electronic control unit 8].

However, if it is determined in step SA3 that the rate of change ΔT/Δt of the driving force is smaller than the predetermined criterion value a, then in step SA5 the rate of change ΔT/Δt of the driving force is It is determined whether or not the value is equal to or greater than the determined criterion value 32. The driving force change speed ΔT/Δt is a predetermined judgment reference value a2 (however,
a2<a.

) or more, the driving force change rate ΔT/Δt is in the medium range, so in step SA6, step B in FIG.

A map is selected, and the differential limiting force Fc is determined from the map B based on the driving force T determined in step SAI. However, if it is determined in step SA5 that the speed of change Δ1/ΔL of the driving force is smaller than the predetermined criterion value a2, the speed of change ΔT/Δt of the driving force is in a relatively gentle region. Therefore, in step SAT, the map C in FIG. A dynamic limiting force F is determined.

Once the differential limiting force Fe is determined in this way, in step SA8, a control signal is output to the control valve 98 so that the differential limiting force FC can be obtained. By repeating the above steps, the differential limiting force F of the differential control clutch 82 is controlled in accordance with the driving force T.

In this embodiment, as described above, when controlling the differential limiting force F, the higher the driving force change rate ΔT/Δt, the rougher the step-like change characteristic.
Since a map representing a relationship in which the step-like change characteristic becomes finer as Δt becomes lower is selected, the differential control clutch 82
The accuracy of differential limiting force control can be increased as much as possible. In other words, in general, when the rate of change in the driving force T is high, pulsations in the driving force T are likely to occur, and the differential limiting force F changes frequently. A hydraulic servo mechanism for actuating the differential control clutch 82 by using a coarse relationship, such as a hydraulic active, the screw 95 of the motor 90 and the control valve 9.
8, while the differential limiting force cannot be changed frequently when the rate of change of the driving force T is small, so there is no problem even if the step-like change characteristic is made finer. By using the step-like change characteristic, the control accuracy of the differential limiting force can be greatly improved.

Next, another application example of the present invention will be described in the flowchart 1-- of FIG.
Explain using.

First, in step S I31, the actual rotation speed of the front wheel 24 is read based on the signals from the front wheel rotation speed sensors 112 and 114, and the rear wheel rotation speed sensor 116 is read.
After the actual rotational speed of the rear wheels 28 is read based on the signal from the
+ is calculated.

In the following step SB2, according to the following equation (4),
From the current front and rear wheel differential rotation speed ΔN F 11 g obtained as described above and the front and rear wheel differential rotation speed ΔNF,lI obtained a predetermined time Δ before, the front and rear wheel differential rotation speed can be calculated. The rate of change ΔNF11/Δt is calculated.

ΔN F11/Δ1=(ΔNFRZ−ΔN,□)/Δ
t... (4) In step SB3, it is determined whether or not the rate of change ΔNPR/Δt of the front and rear wheel differential rotational speeds obtained in step SB2 is equal to or greater than a predetermined criterion value of 8. Ru. Change speed of front and rear wheel differential rotation speed ΔNy++/Δt
is greater than or equal to a predetermined criterion value of 5, the rate of change in the differential rotational speed of the front and rear wheels ΔN Fi
Since this is a relatively steep region of 1/ΔL, step SB4
In this step, map A in FIG. 8 with the roughest step-like change characteristic is selected, and from the map A2, the differential rotational speed ΔN□1 of the front and rear wheels determined in step SBI is determined.
The differential limiting force Fc is determined based on .

A plurality of types of maps are stored in advance in the ROM of the electronic control unit 86.

However, if it is determined in step SB3 that the rate of change ΔNr*/Δt of the front and rear wheel differential rotational speeds is smaller than the predetermined criterion value S, then step S
In B5, the driving force change rate ΔT/Δ[ is a predetermined judgment reference value.

It is determined whether or not. The rate of change ΔNFR/Δt of the differential rotational speed of the front and rear wheels is determined based on a predetermined criterion*(
If it is li'fb2 (however, bz < b+) or more, the change rate ΔNFR/Δ of the front and rear wheel differential rotational speed is in a medium range, so in step SB6, the step-like change characteristic is medium. The rough B2 map of FIG. 9 is selected, and from the B2 map, step SBI
The differential limiting force F is determined based on the front and rear wheel differential rotational speed 1ΔNFM+ determined by . However, - in step SB5, the rate of change ΔN of the differential rotational speed of the front and rear wheels
If it is determined that F11/Δt is smaller than the predetermined judgment reference value b2, the step-like Map 02 in Fig. 10, which has the most detailed change characteristics, is selected, and from that map, the differential limiting force F is calculated based on the front and rear wheel differential rotation speed 1ΔN)*1 determined in step SBI. It is determined.

Once the differential limiting force FC is determined in this way, a control signal is output to the control valve 98 in step SB8 so that the differential limiting force FC can be obtained. Then, the above steps are executed repeatedly.
The differential limiting force F of the differential control clutch 82 is controlled according to the front and rear wheel differential rotation speed 1ΔN□1.

In this embodiment, as in the above-mentioned embodiment, when controlling the differential limiting force Fe, the higher the change rate ΔNFl[/Δt of the front and rear wheel differential rotation speeds, the rougher the step-like change characteristic becomes. Since a map representing a relationship in which the step-like change characteristic becomes finer as ΔN□/Δt becomes smaller is selected, the accuracy of the differential limiting force control of the differential control clutch 82 can be increased as much as possible.

Further, another application example of the present invention will be explained based on flowchart 1 in FIG. 11.

First, in step S01, the steering angle θ (absolute value) of the steering wheel or front wheels 24 (not shown) is read based on a signal from the steering angle detection sensor 102, thereby calculating the steering angle θ.

In the following step SC2, according to the following equation (5),
” - the current steering angle θs2 obtained as described above and the steering angle θ3 obtained a predetermined time Δ before. From this, the rate of change of the steering angle Δθ, /Δt is calculated.

Δθ, /Δ1=(θsz−〇, I)/Δt・・・(
5) In step SC3, it is determined whether the rate of change of the steering angle Δθ, /Δt obtained in step SC2 is equal to or greater than a predetermined criterion value 01. When it is determined that the rate of change in the steering angle Δθ, /Δt is equal to or higher than the predetermined criterion value C1, the rate of change in the steering angle Δθ, /Δt
Since this is a relatively steep region of Δt, map A, 3 in FIG. The differential limiting force Fc is determined based on the steering angle θ. A plurality of types of maps are stored in advance in the ROM of the electronic control unit 86.

1 to 1, if it is determined in step SC3 that the rate of change of the steering angle Δθ,/Δt is smaller than the predetermined criterion value C, then in step SC5,
It is determined whether the rate of change of the steering angle Δθ, /Δt is equal to or greater than a predetermined determination reference value 62. The rate of change of the steering angle Δθ, /Δt is a predetermined judgment reference value C2 (however,
If C2<C) or less, the steering angle change rate Δθ, /Δ
Since this is a medium region of t, map B in Fig. 13, which has a moderately rough step-like change characteristic, is selected in step SC6, and the map B is obtained in step SCI from the map B in Fig. 13. Rudder angle θ.

The differential limiting force FC is determined based on . However, in step SC5, the rate of change of the steering angle is Δθ.

/Δt is smaller than a predetermined determination reference value C2, the rate of change Δθ of the steering angle.

/Δt is a gentle region, so in step SC7, the map 03 in FIG.

From the map, the differential limiting force F is determined based on the steering angle θ determined in step SC1.

Once the differential limiting force F is determined in this way, a control signal is output to the control valve 98 in step SC8 so that the differential limiting force 1+c is obtained. By repeating the above steps, the differential limiting force F of the differential control clutch 82 is controlled according to the steering angle θ.

In this embodiment as well, as in the previous embodiment, when controlling the differential limiting force F, the higher the steering angle change rate ΔθS/Δt, the rougher the step-like change characteristic becomes.
Since a map representing a relationship in which the step-like change characteristic becomes finer as θ and /Δt become lower is selected, the accuracy of the differential limiting force control of the differential control clutch 82 can be increased as much as possible.

In the above embodiment, when controlling the differential limiting FC, the map corresponding to the rate of change of the vehicle running condition parameter is selected. Based on the relationship ΔT/Δt of the actual driving force, the horizontal width ΔI4T that maintains the change in differential limiting force F, and the rise width Δ■1 that causes a sudden change in differential limiting force FC are determined. determine their horizontal width Δl
A relationship having a step-like change characteristic in which IT and vertical width ΔF'ct are alternately provided may be determined in advance, as shown in FIG. 17, for example. Similarly, based on the pre-stored relationship shown in FIGS. 18 and 19, the horizontal width ΔI( Determine N and the rise width Δ■o that causes the differential limiting force F to suddenly change, and create a relationship that has a step-like change characteristic with alternating horizontal width ΔHT and rise width ΔFCT. For example, as shown in Fig. 20, it may be determined in advance.In the above embodiment, the horizontal widths ΔToa and ΔHH that maintain the change in the differential limiting force FC are the changes in the differential limiting force F. The rising width Δ■ that rapidly changes the differential limiting force FC corresponds to the suppression region in which the differential limiting force F is suppressed, and the rising width Δ■ 8 corresponds to the changing region that rapidly changes the differential limiting force F.

One application example of the present invention has been described above based on the drawings, but
The invention also applies in other aspects.

For example, in the suppression region in the embodiment described above, the differential limiting force F was maintained at a constant value, but it may be suppressed to a state where it changes gradually.

Furthermore, in the above embodiment, a so-called full-time four-wheel drive vehicle was described, but a so-called bar l-drive vehicle equipped with a switching clutch that switches between a four-wheel drive state and a two-wheel drive state is described.
The present invention is also applicable to controlling the switching clutch in a Type 1 type four-wheel drive vehicle.

Furthermore, in the above-mentioned embodiments, the step-like change characteristic was roughly or finely changed in relation to the speed of change of the vehicle driving condition parameter, but such a change was made only for the region of the step-like change characteristic. may be added.

Note that the above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of an application example of the present invention. FIG. 2 is a diagram illustrating the clutch oil pressure control circuit of FIG. 1. FIG. 3 is a flowchart 1- explaining the operation of the application example of FIG. Figures 4, 5, and 6
The figure shows the relationship obtained in relation to the rate of change of the driving force by the operation of FIG. 3. FIG. 7 is a diagram corresponding to FIG. 3 showing the operation of another application example of the present invention,
FIG. 8, FIG. 9, and FIG. 10 are diagrams showing the relationships obtained in relation to the rate of change of the front and rear wheel differential rotational speeds by the application example of FIG. 7, respectively. FIG. 11 is a diagram corresponding to FIG. 3 showing the operation of another application example of the present invention, and FIG.
13 and 14 are diagrams showing relationships obtained in relation to the steering angle change speed by the application example of FIG. 11, respectively. 15 and 16 respectively show the relationships for determining the horizontal width and rising width in other application examples of the present invention, and FIG. 17 shows the relationship determined from FIGS. 15 and 16. FIG. 4 is a diagram showing a relationship determined in advance based on the horizontal width and rising width. Figure 18, 1st
9 and 20 are diagrams corresponding to FIG. 15, FIG. 16, and FIG. 17, respectively, in other application examples of the present invention. Fig. 2 24: Front wheel 28: Rear wheel 82: Differential control clutch

Claims (1)

[Scope of Claims] In a front and rear wheel drive vehicle equipped with a differential control clutch that adjusts differential rotational speeds between front wheels and rear wheels, a suppression region that suppresses changes in differential limiting force of the differential control clutch. A control method for controlling the differential limiting force based on a vehicle running state parameter based on a relationship having a step-like change characteristic that alternately has change regions in which the differential limiting force is rapidly changed, When the speed of change of the driving condition parameter increases, the stepwise change characteristic of the relationship is made rougher, and when the speed of change of the driving condition parameter decreases, the stepwise change characteristic is made finer. A method of controlling a differential control clutch for front and rear wheel drive vehicles.